[llvm-bugs] [Bug 25592] New: [dagcombine] redundant 'and' of phi node not removed during isel

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=25592

            Bug ID: 25592
           Summary: [dagcombine] redundant 'and' of phi node not removed
                    during isel
           Product: libraries
           Version: trunk
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: gberry at codeaurora.org
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

SelectionDAGBuilder seems to remove redundant 'and' nodes in some cases but not
others.

test/CodeGen/AArch64/free-zext.ll has two cases that demonstrate this.  The
first, test_free_zext3 demonstrates that the 'and' made redundant by
CodeGenPrepare (in bb3) is removed.  In the second test, test_free_zext4, the
'and' of the phi value in the loop block is not removed.  See the TODO comment
in this test for a CHECK-NOT that can be enabled if this issue is resolved.

This issue was discovered during development of the following change:
http://reviews.llvm.org/D14584

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